1. Field of the Invention
In general, the present invention relates to counterbalance systems that are used to hold the sashes of a window open. More particularly, the present invention relates to counterbalance systems that are used in window assemblies having side-loading sashes.
2. Prior Art Description
There are many types of windows used in modern construction. Some windows are designed to open, some are not. Of the windows that are designed to open, some windows have sashes that open vertically and others have sashes that slide open laterally, or rotate outwardly.
Windows that have vertically opening sashes are the most common window used in residential home construction. Vertically opening windows are either single-hung, having one sash that opens, or double-hung, having two sashes that open. In both single-hung and double-hung windows, the same system is used to hold a window sash up once it is open. If no system is used, gravity causes the sash of the window to close as soon as it is opened and released.
In low quality windows, friction between the window sash and the window frame is relied upon to hold a sash open. Such a system is highly unreliable because the friction relied upon varies as parts wear, expand, contract and are painted. It is for this reason that most single and double-hung windows are manufactured with counterbalance systems.
Early window sash counterbalance systems were simply weights that were attached to the sash. The weights were attached to a sash by a rope or chain that passed over a pulley at the top of the window frame. Such old counterbalance systems are exemplified by U.S. Pat. No. 3,160,914 to Brienza, entitled Sash Weight Mounting Means. Such counterbalance systems required window wells in which the weights move. Accordingly, such windows were difficult to insulate. Additionally, the rough opening needed for the window had to be much larger than the window sashes. Finally, window sashes attached to such counterbalance systems could not be tilted for cleaning or otherwise removed from the window frame.
Recognizing the many disadvantages of window well counterbalance systems, windows were manufactured with spring loaded counterbalance systems. Spring loaded counterbalance systems relied upon the pulling strength of a spring, rather than a hanging weight, to counterbalance the weight of a window sash. Accordingly, window wells for weights were no longer required.
Counterbalancing a window sash with a coil spring is a fairly simple matter. One end of the coil spring is attached to the window frame while the body of the coil spring is engaged by the sash. One of the simplest examples of a coil spring counterbalance system is shown in U.S. Pat. No. 2,732,594 to Adams, entitled Double Hung Window Sash. The difficulties with such a system occur when a window manufacturer wants to use coil springs to counterbalance a window sash while simultaneously making a window tiltable or removable for cleaning.
In modern tilt-in windows, the window sash tilts for cleaning but never completely leaves the window frame. Counterbalancing such windows can, therefore, be accomplished by attaching coil springs to the end of the window sash that never leaves the frame.
Counterbalancing a window with a sash that is removable is far more difficult. In a window with a removable sash, the counterbalance system must have the ability to connect and disconnect from the sash. The counterbalance system commonly used for a side loading window with a removable sash is a “block and tackle” counterbalance. A block and tackle counterbalance contains pulleys, string and a spring that maintains tension on the string. The end of the string is typically attached to the window sash with a clip. When a window sash is being removed completely from a window frame, the clip must be manually detached from the sash. Once detached, the sash can be removed while the block and tackle counterbalance system remains behind in the jamb of the window frame. Prior art block and tackle counterbalance systems are exemplified in U.S. Pat. No. 6,745,433 to Newman, entitled Side Load Balance Cord Terminal Clip; U.S. Pat. No. 4,697,304 to Overgard, entitled Friction Controlled Window Balance, and U.S. Pat. No. 4,089,085 to Fitzgibbon, entitled Sash Balance and Components Thereof.
There are many problems associated with prior art block and tackle counterbalance systems. First, a block and tackle counterbalance system must be custom designed to correspond to a particular window sash height and/or weight. Different block and tackle counterbalance assemblies must therefore be manufactured to accommodate sashes of different sizes and different weights. Furthermore, block and tackle counterbalance systems are complex assemblies that contain several moving parts. These parts are difficult to assemble and are subject to failure over time. Consequently, block and tackle counterbalance systems tend to be expensive to manufacture and have limited reliability. Another disadvantage of block and tackle counterweight assemblies is that they are difficult to detach and reattach to a window sash and can easily cause injury to an inexperienced person who attempts the task.
A need therefore exists for a counterbalance system that can be used in a window assembly with a side loading sash, wherein the counterbalance system does not use a complex block and tackle construction, is versatile to many window sizes, is simple to attach and detach, and is both simple and inexpensive to manufacture. This need is met by the present invention as described and claimed below.